LONDON, Oct 12 (Reuters) - The top three oil-dependent sovereign wealth funds have been selling European equity holdings since May, a study showed on Monday, another sign of petrodollars being withdrawn from world markets.

However, Asian funds have continued to add European equities, according to the data from Nasdaq Advisory Services, which provides analysis on shareholder and investor activity.

Since May, the Saudi Arabian Monetary Authority has sold $1.2 billion worth of equities across Nasdaq’s European client base. That accounts for 13 percent of its $9.2 billlion holdings in the European companies tracked by Nasdaq.

Norway’s Norges Bank Investment Management has sold $1.1 billion - around 2 percent of the $57.5 billion market value of its holdings. The Abu Dhabi Investment Authority has cut some $300 million worth of shares from its $3.6 billion holding.

“Over 2015, the three largest oil-dependent SWFs have all been reducing their equity holdings in the region, with this trend accelerating over the second quarter and into the third quarter of the year,” said Alexander Free, an analyst with Nasdaq’s Advisory Services.

The data is based on a sample of 159 European companies, with a market value of $1.87 trillion, Nasdaq says. They range from retail and telecoms shares to financials and utilities.

Falling oil prices - with Brent crude down over 60 percent since summer 2014 - has put pressure on oil producers to rein in spending or liquidate assets.

Energy-exporting countries pulled money out of world markets last year for the first time in almost two decades, halting the “recycling” of oil windfalls, BNP Paribas has said. The trend would continue as energy prices stayed under pressure, the bank predicted last year.

In July, Saudi Arabia resorted to issuing a bond for the first time since 2007. The International Monetary Fund has warned of the Saudi deficit - estimated at around 20 percent of GDP this year.

The Saudi central bank, which serves as the wealth fund of the world’s top oil exporter, has been drawing down its reserves since late 2014. Its net foreign assets fell by $6.6 billion in August as the Saudis liquidated assets to plug the budget gap .

“It’s a pretty dire situation,” Free said.

Norway has announced it will make its first net withdrawal from its sovereign fund since it was set up, to help pay for tax cuts designed to stimulate the economy. Its $830 billion fund is the world’s largest, holding about 1.3 percent of global stocks.

In contrast, the three biggest non-commodity driven sovereign funds have been net buyers of European equities - particularly China’s SAFE, which holds about $35.6 billion worth of the Nasdaq sample.

SAFE started buying heavily in Europe from the first quarter of 2015, acquiring $2.1 billion of the shares tracked by Nasdaq. Singapore’s Temasek and GIC have also acquired a combined $1.1 billion of European equities so far this year, Free said.

He suggested their interest may stem from a search for better valuations as U.S. equity prices surged to pre-crisis levels, while the European Central Bank’s money-printing programme also lent support.